The RNLI is urging people to take extra care around sand dunes this summer, after a two metre deep tunnel was discovered on a Cornwall beach.

Lifeguards managed to fill the tunnel at Constantine before anybody was hurt, but the charity is urging people to be extra careful around the unstable dunes as the warmer weather creates increased risk of collapse.

RNLI lifeguards at Constantine beach discovered the tunnel that had been dug into the side of a sand dune on Tuesday. It was unattended and there was a backpack inside it. The tunnel was roughly two metres deep and one metre high, so could have been accessed by a small child. The lifeguards filled in the hole using shovels to prevent anybody from getting trapped.

Many sand dunes on Cornwall’s beaches have altered dramatically over the last 12 months due to the winter storms and in the hot temperatures the sand dries creating an increased risk of collapse.

Steve Instance, RNLI senior lifeguard manager, said: "This is the first sand tunnel we’ve seen this year and fortunately the lifeguards spotted it and were able to cover it over quickly. Clearly it could have collapsed at any time whilst digging it or even whilst walking over it with potentially fatal consequences.

"Although the large cliffs of sand may look enticing play grounds, we urge people to resist the temptation to play on them or dig into them. The sand is very unstable and can collapse at any time, trapping anyone on or below it. The areas of unstable dunes and cliffs are clearly signed on the beaches and we ask people to take heed of this advice as it’s in their best interests for their safety.’"

RNLI lifeguards begin their peak season patrols from tomorrow, Saturday, July 5, meaning all 57 lifeguarded beaches in Cornwall will be patrolled, with lifeguard numbers increasing on some of the busier beaches.

Peak season runs until September 7 and is predicted to be the busiest time for RNLI lifesavers as it encompasses the school summer holidays. Anybody visiting the coast should visit an RNLI lifeguarded beach and swim between the red and yellow flags, which marks out the safest bathing area on the beach.